In a hydraulic damper of a multi-cylinder type in general, a rod guide for respectively closing an opening end of a cylinder and an opening end of an outer cylinder enclosing the cylinder, and for supporting a rod inserted inside the cylinder in a freely slidable manner is provided. Further, a ring-shaped insert metal having sealing members to each of an inner periphery and an outer periphery thereof is layered on this rod guide so as to maintain oil tight property of the hydraulic damper.
In detail, the insert metal is provided with, at the outer periphery side thereof, a ring-shaped seal contacting against the inner periphery of the outer cylinder, and at the inner periphery side thereof, an oil lip and a dust lip slidably contacting with the outer periphery of the rod, so as to seal between the respective rod and the outer cylinder with the insert metal in the oil tight manner.
In such a hydraulic damper of a multi-cylinder type, since the sliding clearance between the rod and the rod guide is not in a perfectly sealed state, the working fluid from an oil chamber inside the cylinder flows into a receiving space between the rod guide and the insert metal through the sliding clearance although little by little. It is required to return this leaked working fluid to a reservoir inside the hydraulic damper, therefore, a communicating hole for communicating the receiving space and the reservoir is provided to the rod guide.
According to JP 2003-343633A, there has been proposed to provide a check valve for only allowing the flow of the working fluid from the receiving space towards the reservoir to prevent the reverse flow of the gas inside the reservoir to the oil chamber in the cylinder through this communicating hole, the receiving space, and further through the sliding clearance.